faye-websocket

This is a general-purpose WebSocket implementation extracted from the
Faye project. It provides classes for easily
building WebSocket servers and clients in Node. It does not provide a server
itself, but rather makes it easy to handle WebSocket connections within an
existing Node application. It does not provide any
abstraction other than the standard WebSocket
API.

It also provides an abstraction for handling
EventSource connections, which are
one-way connections that allow the server to push data to the client. They are
based on streaming HTTP responses and can be easier to access via proxies than
WebSockets.

Installation

$ npm install faye-websocket

Handling WebSocket connections in Node

You can handle WebSockets on the server side by listening for HTTP Upgrade
requests, and creating a new socket for the request. This socket object exposes
the usual WebSocket methods for receiving and sending messages. For example this
is how you'd implement an echo server:

WebSocket objects are also duplex streams, so you could replace the
ws.on('message', ...) line with:

ws.pipe(ws);

Note that under certain circumstances (notably a draft-76 client connecting
through an HTTP proxy), the WebSocket handshake will not be complete after you
call new WebSocket() because the server will not have received the entire
handshake from the client yet. In this case, calls to ws.send() will buffer
the message in memory until the handshake is complete, at which point any
buffered messages will be sent to the client.

If you need to detect when the WebSocket handshake is complete, you can use the
onopen event.

If the connection's protocol version supports it, you can call ws.ping() to
send a ping message and wait for the client's response. This method takes a
message string, and an optional callback that fires when a matching pong
message is received. It returns true iff a ping message was sent. If the
client does not support ping/pong, this method sends no data and returns
false.

Using the WebSocket client

The client supports both the plain-text ws protocol and the encrypted wss
protocol, and has exactly the same interface as a socket you would use in a web
browser. On the wire it identifies itself as hybi-13.

The WebSocket client also lets you inspect the status and headers of the
handshake response via its statusCode and headers properties.

Subprotocol negotiation

The WebSocket protocol allows peers to select and identify the application
protocol to use over the connection. On the client side, you can set which
protocols the client accepts by passing a list of protocol names when you
construct the socket:

protocols is an array of subprotocols as described above, or null.
options is an optional object containing any of these fields:

headers - an object containing key-value pairs representing HTTP headers to
be sent during the handshake process

maxLength - the maximum allowed size of incoming message frames, in bytes.
The default value is 2^26 - 1, or 1 byte short of 64 MiB.

ping - an integer that sets how often the WebSocket should send ping
frames, measured in seconds

WebSocket API

Both server- and client-side WebSocket objects support the following API.

on('open', function(event) {}) fires when the socket connection is
established. Event has no attributes.

on('message', function(event) {}) fires when the socket receives a
message. Event has one attribute, data, which is either a String
(for text frames) or a Buffer (for binary frames).

on('error', function(event) {}) fires when there is a protocol error
due to bad data sent by the other peer. This event is purely informational,
you do not need to implement error recover.

on('close', function(event) {}) fires when either the client or the
server closes the connection. Event has two optional attributes,
code and reason, that expose the status code and message
sent by the peer that closed the connection.

send(message) accepts either a String or a Buffer and sends a
text or binary message over the connection to the other peer.

ping(message = '', function() {}) sends a ping frame with an
optional message and fires the callback when a matching pong is received.

close(code, reason) closes the connection, sending the given status
code and reason text, both of which are optional.

version is a string containing the version of the WebSocket
protocol the connection is using.

protocol is a string (which may be empty) identifying the
subprotocol the socket is using.

Handling EventSource connections in Node

EventSource connections provide a very similar interface, although because they
only allow the server to send data to the client, there is no onmessage API.
EventSource allows the server to push text messages to the client, where each
message has an optional event-type and ID.

The send method takes two optional parameters, event and id. The default
event-type is 'message' with no ID. For example, to send a notification
event with ID 99:

es.send('Breaking News!', {event: 'notification', id: '99'});

The EventSource object exposes the following properties:

url is a string containing the URL the client used to create the
EventSource.

lastEventId is a string containing the last event ID received by the
client. You can use this when the client reconnects after a dropped
connection to determine which messages need resending.

When you initialize an EventSource with new EventSource(), you can pass
configuration options after the response parameter. Available options are:

headers is an object containing custom headers to be set on the
EventSource response.

retry is a number that tells the client how long (in seconds) it
should wait after a dropped connection before attempting to reconnect.

ping is a number that tells the server how often (in seconds) to
send 'ping' packets to the client to keep the connection open, to defeat
timeouts set by proxies. The client will ignore these messages.

For example, this creates a connection that allows access from any origin, pings
every 15 seconds and is retryable every 10 seconds if the connection is broken:

You can send a ping message at any time by calling es.ping(). Unlike
WebSocket, the client does not send a response to this; it is merely to send
some data over the wire to keep the connection alive.

License

(The MIT License)

Copyright (c) 2010-2013 James Coglan

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the 'Software'), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.